So if you look a a boat and see the chainplates topside and there is no way to see any attachment below is their any other way they could have been built that doesn't use a knee or bulkhead or exterior bolts through the hull and is NOT glassed in?

IOW is their any construction method where the chainplates are flush or nearly flush with the hull interior and still allows inspection.

I ground out my chainplates and re-glassed them in, after shortening them a little. I cut off the high stress area where it goes through the deck.

The crazing on your hull looks like water got in the chainplate pocket and froze, many years in a row. I have heard some folks drill a small hole in the pocket on the inside to allow water to drain out. The builder just glassed over the chainplate so there is plenty of room for water where the glass makes a radius over the edges of the steel chainplates. No way to know how it is in there unless you cut it out and inspect. It's perfect conditions for crevice corrosion.

FWIW I spent a lot of time discussing the plates and how to fix or re=-install with both Maine Sail and Jeff_H, neither of which is a lightweight when it comes to stuff like this.

Neither of them had knowledge of the shape of the plates prior to today - all I could tell them was that a horizontal band/tab was involved, but no through bolts etc.

Titanium is one of the the things I'm looking at, the could be thinner in all dimensions.
Science has moved on since 1987, I have a LOT more options than "drill through the existing and bolt new ones on the outside" - that's the first and last option according to the Irwin 'expert' - a Mr. Gene Gammon.
I prefer taking advice from someone that does not tell me to leave the possibly rusting old ones in place as backing plates.

I'm still thinking- I might go with a hybrid inner/outer.
I have to rebuild the 'furniture', i.e. book shelves, I do not have to rebuild them they way they were.

Simplest solution is on the outside of the hull. Without a bulkhead in each plate's location there are no other options I can see except the original method. That was probably the reason it was done this way to start with - without knees which would have been in the way of interior cabinetry or bulkheads at the right place it allows placement anywhere the builder wanted.

I would say the simplest solution would be to put them back where they were on the inside of the hull but bolt them through the hull rather than glassing them in place.

On that boat putting them on the outside would present big problems because of the heavy cap rail and rub rail.

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.

I'm envisioning a way to make new chain plates that will be removable for inspection but be similar to the existing ones.

Let me see if I can explain in words what should be a drawing.

Glass with epoxy two or three horizontal stainless plates about the same way the current T crosses are glassed in.
The difference is that they are glassed in such a way so their is a slot left in the middle wide enough so the vertical chain plate can be slipped up under each horizontal strap and out through the slot in the cap rail.
Now just use flat head machine screws through the horizontal straps and tapped into the vertical chain plates.

The bottom of the chain plate can have a doubler piece welded on as a stop against the bottom horizontal piece.

The whole thing can have an inspection cover over it so it can be inspected.
The horizontal pieces glassed in should never get wet and last indefinitely.
The vertical piece can just be unscrewed and withdrawn and the critical part just below the cap rail inspected.

In any event even if water did get in it would not be trapped in a pocket.

Any concern about the strength of the machine screws can be engineered away by simply changing the size of the vertical member. It can be wider or thicker under the cap rail if you need more screw area and the existing width above the cap.

This would be a modest increase in cost mostly labor to deal with drilling and tapping a couple dozen screws rather than welding.

I would say the simplest solution would be to put them back where they were on the inside of the hull but bolt them through the hull rather than glassing them in place.

On that boat putting them on the outside would present big problems because of the heavy cap rail and rub rail.

I've seen a few boats where the external chain plates curve around the cap rail and rub rail. I don't believe this is ideal. I wonder if you couldn't just cut a slot in the cap and rub rails so the external chain plates would be flush with the hull and pass through the slot. You could leave a little extra space, a few mm, in the slot so water would run down and out of the slot, on the outside of the hull. With some SS backing plates you'd have a pretty bulletproof system you could inspect visually and service easily.

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